Prospective Fault Displacement Hazard Assessment for Leech River Valley Fault Using Stochastic Source Modeling and Okada Fault Displacement Equations
Round 1
Reviewer 1 Report
This paper develops an alternative method for probabilistic fault displacement hazard analysis based on stochastic source modeling and analytical formulations to assess elastic dislocations due to earthquake rupture. The manuscript presents an impressive piece of work stemming from an analysis of the Leach Valley fault near Victoria, British Columbia, Canada. This study attempts to characterize the uncertainty in the occurrence of fault ruptures using location, geometry, and slip distribution, and employs the so-called Okada equation to calculate surface fault displacement. The method is compatible with probabilistic seismic hazard analysis based on fault sources, and the estimation of potential rupture areas can be achieved through Monte Carlo simulations, which can be considered through statistical models. But in general, the purpose of this study can be used to assess differential displacement caused by fractures at multiple locations simultaneously. However, the authors must account for the interaction between the fault systems, and the estimated rupture probability may be more reliable for the Leech River Valley fault. I feel this study might be interesting for publication in GeoHazard, but a comparison of the different methods used and data analysis is still lacking. The paper requires a lot of work to make it technically sound. Here are some points for improvement:
- The authors emphasize that the uncertainty of quantifying the risk of fault displacement is crucial to effectively manage potential damage and losses, but the slip rate and possible stress drop range of the fault are not accounted for, which will be reserved for the interpretation of the final results.
- The method proposed in this study uses stochastic source modeling and the Okada equation, instead of the empirical prediction equation in the traditional method, to evaluate the potential fault displacement hazards caused by earthquake rupture, but how to use the Okada equation for the process of stochastic source modeling? However, it is not clearly presented, and the uncertainty analysis is not clearly explained, which needs to be strengthened and supplemented.
- Evaluating site-specific fault displacement and differential fault displacement hazard curves for multiple sites within the fault rupture zone shows that relatively large displacements (~0.5 m vertical) can be expected at a low probability level of 10-4, is it possible to consider the effect of the slip rate of the fault in this case? Although the authors show that the low probability of a major fault displacement hazard is attributed to the low seismicity of the LRVF (i.e. the average recurrence period for moderate earthquakes is about 1000 year).
- For infrastructure that crosses faults, it is very important to assess the structural integrity for the possible differential fault displacement risk, but whether this result takes into account the strong ground motion caused by the weak fault zone? After all, some fault activities do not rupture to the surface, but strong ground motions can cause damage to infrastructure.
- It is crucial to apply this method to more historical events in this area, as it may require some parameters to be adjusted to obtain reasonable results. Because such analyses are lacking in this paper.
- The fault parameters and weights of LRVF are stated in Table 1. Although the literature of [26] is used, the authors have not explained how to choose this model. If the values ​​change slightly, will there be large differences in results?
- Why the fault size can only take odd multiples of the sub-fault size (= 2 km), i.e. 2, 6, 10, etc. Please explain it clearly.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Very well done. Congratulations
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Most of the issues in this article have been corrected and the current status of this article is acceptable.
Author Response
Thank you very much for reviewing the manuscript again. I appreciate your time.
